Seated Bent-Over One-Arm Dumbbell Triceps Extension
The seated bent-over one-arm dumbbell triceps extension is an isolation exercise where you sit bent forward at the hips and extend one arm straight back, working your triceps through a kickback-style motion with the support of the bench underneath you. It isolates the triceps without any help from your shoulders or chest, since your upper arm stays fixed and only your elbow moves. It suits lifters who want focused triceps work with a stable base to brace against.
Why it works
Keeping your upper arm parallel to the floor and fixed in place removes your shoulder from the movement almost entirely, leaving your triceps as the only muscle responsible for straightening your elbow against the dumbbell's resistance. Sitting and bending at the hips, rather than standing, gives you a stable surface to brace your free hand or forearm against, which takes balance out of the equation and lets you focus the effort entirely on the extension itself. That isolation is what makes this variation a precise way to target the triceps without other muscles taking over the work.
Set up
- Sit on the edge of a bench, holding a dumbbell in one hand.
- Bend forward at your hips until your torso is roughly parallel to the floor, bracing your free hand on your knee or the bench.
- Raise your upper arm so it's parallel to the floor, with your elbow bent at 90 degrees and the dumbbell hanging down.
How to do it
- Keeping your upper arm still, extend your elbow to straighten your arm fully behind you.
- Squeeze your triceps at the top of the movement.
- Slowly bend your elbow back to the starting position, controlling the dumbbell the whole way.
- Complete all reps on one side before switching arms.
Form cues
- Keep your upper arm pinned in place; only your forearm should move.
- Fully straighten your arm at the top without locking the elbow harshly.
- Keep your back flat rather than rounding forward as you extend.
- Move slowly enough to control the dumbbell on the way back down.
Breathing: Exhale as you extend your arm back, and inhale as you bend your elbow to return.
Common mistakes
Letting the upper arm drop or swing during the extension.
Fix: Brace your upper arm against your side or hold it fixed with your free hand if needed, so only your forearm moves.
Using momentum to swing the dumbbell up.
Fix: Slow the tempo down and focus on a controlled contraction rather than a fast, jerky motion.
Rounding the back to compensate for a heavy dumbbell.
Fix: Choose a lighter dumbbell and keep your spine flat throughout the set.
Only partially extending the arm each rep.
Fix: Straighten your arm fully at the top of each rep to get the complete range of motion.
How to program it
- As a light isolation exercise, 2 to 3 sets of 10 to 15 reps per arm, done after your main pressing work, fits well in most upper-body sessions.
- Pair it with a compound push movement like a bench press or overhead press earlier in the session, since your triceps will already be somewhat fatigued from those lifts.
- Progress by adding small amounts of weight only once you can complete every rep with a full, controlled range of motion.
Safety notes
- Choose a dumbbell light enough that your upper arm stays still throughout the set.
- Avoid locking the elbow out harshly at the top; a controlled straightening is enough to fully engage the triceps.
- Stop if you feel strain in your shoulder rather than your triceps, which usually means the upper arm is moving instead of staying fixed.
Exercise profile
- Force
- Push
- Mechanics
- Isolation
- Category
- Strength
Frequently asked questions
How many reps should I do?
10 to 15 reps per arm for 2 to 3 sets works well for this isolation exercise, since it's meant to finish off the triceps rather than build maximal strength.
Why does this only work one arm at a time?
Training one arm at a time lets you brace your body against the bench and focus fully on keeping the working arm still, which improves the isolation compared to moving both arms together.
What if I don't have a bench to sit on?
You can do the same movement standing and bent over at the hips, though you'll need more core and hip control since you lose the bench's support.
My elbow feels this more than my triceps. What's wrong?
Check that you're using a weight you can control through a full range of motion; a weight that's too heavy often shifts stress toward the elbow joint instead of the triceps muscle.